Re: [time-nuts] Holdover: Z3801A vs KS-24361
Hi There isn’t much you can really see on a GPSDO comparing it to a normal OCXO. The OCXO simply is not accurate enough. You need something like a Cs standard, a different GPSDO, or a good Rb for the reference. (Yes, if you have a hydrogen maser, you *can* use that ….). First thing to check is the DAC readings on the unit …. Bob > On Apr 15, 2018, at 6:59 AM, Hal Murray wrote: > > > kb...@n1k.org said: >>> A KS-24361 says: >>> Predict 394.1 us/initial 24 hrs >> That would suggest the unit is unlocked. It should be below 10 us. Just as >> with the 3801, the estimate is a bit fuzzy. You should be able to see issues >> in the data on the Z3809/Z3810. > > It says it is locked and has been locked for days. >>> Locked to GPS TFOM 3 FFOM 0 > > I used this as a learning exercise for my new TICC. Something is clearly > fishy. > > The reference for the TICC is the crystal in a HP 5334B with the good-crystal > option. It's not calibrated, but there isn't any GPS logic to jerk it > around. I assume the swing is due to temperature. I corrected the slope of > the graph by hand. > > Here is a day+ of data: > http://users.megapathdsl.net/~hmurray/time-nuts/TICC/TICC-KS.png > > Here is a zoomed in chunk: > http://users.megapathdsl.net/~hmurray/time-nuts/TICC/TICC-KS-2.png > > > -- > These are my opinions. I hate spam. > > > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Holdover: Z3801A vs KS-24361
kb...@n1k.org said: >> A KS-24361 says: >> Predict 394.1 us/initial 24 hrs > That would suggest the unit is unlocked. It should be below 10 us. Just as > with the 3801, the estimate is a bit fuzzy. You should be able to see issues > in the data on the Z3809/Z3810. It says it is locked and has been locked for days. >> Locked to GPS TFOM 3 FFOM 0 I used this as a learning exercise for my new TICC. Something is clearly fishy. The reference for the TICC is the crystal in a HP 5334B with the good-crystal option. It's not calibrated, but there isn't any GPS logic to jerk it around. I assume the swing is due to temperature. I corrected the slope of the graph by hand. Here is a day+ of data: http://users.megapathdsl.net/~hmurray/time-nuts/TICC/TICC-KS.png Here is a zoomed in chunk: http://users.megapathdsl.net/~hmurray/time-nuts/TICC/TICC-KS-2.png -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Holdover: Z3801A vs KS-24361
Hi > On Apr 12, 2018, at 1:30 AM, Hal Murray wrote: > > On that Status page, A Z3801A says: > Predict 2.5 us/initial 24 hrs That sounds about right for a 3801. The prediction is something better than a wild guess and not what one would call a solid number. > > A KS-24361 says: > Predict 394.1 us/initial 24 hrs That would suggest the unit is unlocked. It should be below 10 us. Just as with the 3801, the estimate is a bit fuzzy. You should be able to see issues in the data on the Z3809/Z3810. A prediction of < 1 can pop up on occasion, on either unit. More typical estimates are in the “couple of us” range. If you yank the antenna, it still does a respectable ~5 us / 24 hrs or so either way. > > Both have been running for weeks. > > Is anybody seeing similar? no > > > Also, the Satellite Status area has a header of SS on the Z3801A and C/N on > the KS. Does anybody know the units and/or what that is actually measuring? There are tables that translate the Motorola (and some of the other brands) status numbers into rough dbc/ Hz. I would not count on the numbers on a 20+ year old design lining up directly with the latest and greatest modern module. Apparently the SNR calculations are a bit weird. Bob > > -- > These are my opinions. I hate spam. > > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
